1. Field of the Invention
This invention concerns nails having a shank portion whose cross-sectional configuration is multi-vaned for providing greater holding power in wooden substrates.
2. Description of the Prior Art
Nails whose shank portions are of star-shaped cross-sectional profile, characterized in having about five pointed vanes, provide greater holding power when joining wooden members. Such nails further possess greater rigidity, and require less material than nails of circular profile having the same effective shank diameter and length.
Despite their known advantages, practical methods for the fabrication of star-profile nails have been elusive. In one general approach, disclosed by Frank Potucek in his U. S. Pat. Nos.: 4,800,746 and 4,833,906, a continuous length of nail-forming wire stock is fed to a first set of rollers that imparts a polygonal cross-section to the wire, and successively to a second set of rollers which converts the polygonal surfaces to vanes. Repeating sections of the wire remain non-formed or skipped. The wire is then severed at said skipped sections and shaped into the nail head or point.
A serious problem with the Potucek technique is that, every time the wire is severed and a head is formed, the advancing and forming mechanism must be stopped. Since the forming rollers are of considerable size and weight, the high frequency start/stop phenomenon produces an oscillating inertial load of very high force amplitude. Such forces are sufficient to cause rapid wear and malfunction of equipment components.
In efforts to overcome the Potucek start/stop problem, it has been sought to merely sever the Potucek formed wire at the skipped spaces, and subsequently form heads on the severed wire segments. Such action would not necessitate stoppage of the roll-forming operation. However, it has been found to be extremely difficult to grip a short piece of star-profile wire with sufficient force to permit a head to be shaped at one extremity.
It is accordingly an object of the present invention to provide a practical process for the manufacture of star-profile nails.
it is another object of this invention to provide a process as in the foregoing object which is substantially continuous in producing star-profile nails from a coil of wire of circular cross section.
It is a further object of the invention to provide apparatus useful in a nail-forming process of the aforesaid nature.
These and other beneficial objects and advantages will be apparent from the following description.